rbx_xml is slow!

[LPGhatguy]

Using an rbxlx version of the open source version of Miner's Haven as a benchmark.

$ cat decode.lua
remodel.readPlaceFile("minershaven.rbxlx")

$ time remodel decode.lua
real    0m24.496s
user    0m0.000s
sys     0m0.000s

$ du -sh minershaven.rbxl minershaven.rbxlx
7.6M    minershaven.rbxl
143M    minershaven.rbxlx

We might be able to recover some time switching to quick-xml, according to some profiling done by @Kampfkarren. Further investment in the binary format is the end-all solution to this, however.